1. Field of the Invention
The present invention relates to fluid powered actuators or motors, and more particularly, to actuators for operating valves such as ball valves or butterfly valves in which the valve element is rotated to open or close the flow passageway through the valve body.
Many types of pneumatic and hydraulic actuators have been designed for automatically operating various types of valves and other similar devices. In such actuators it is desirable that they have a low profile and, in general, occupy a minimum amount of space; additionally it is advantageous to minimize the number of parts needed to connect the valve to the actuator mechanism thus minimizing the space occupied by the combined valve-actuator system. It is also desirable to devise a mechanism in which the valve and/or the parts which connect the valve stem to the actuator mechanism are protected or shielded.
The actuator of the present invention accomplishes these results by means of its novel construction and manner of connection to the valve.
2. Description of the Prior Art
U.S. Pat. No. 2,957,361 to Herbenar discloses an actuator for a power steering mechanism. The actuator in question comprises a cylinder having two pistons therein which can move simultaneously toward and away from the middle of the cylinder. Each piston has a skirt extending toward the center of the cylinder and these skirts are located on radially opposite sides of the cylinder. The skirts have gear racks on their inner surfaces which operate a pinion wheel mounted on a shaft extending transversely through the cylinder.
One of the problems of the actuator shown in the Herbenar patent is that the porting systems which provide hydraulic or pneumatic fluid to the cylinder are comprised of tubes located externally of the cylinder. These tubes increase the profile of the actuator and, being relatively small and fragile, are subject to breakage and damage. Another problem is that a relatively complicated mechanism is used to connect the actuator shaft to another shaft which is to be turned by the actuator. This further increases the profile of the mechanism.
U.S. Pat. No. 3,107,080 to Priese discloses a fluid powered actuator for a ball valve in which the porting systems are internal to the actuator cylinder or housing. However the passageways which supply fluid to the ends of the cylinder discharge almost directly between the ends of the cylinder and the end plates making the device subject to leakage. Furthermore the actuator shaft and the valve stem to be turned thereby are one integral piece. The relative inflexibility of this arrangement together with orientation of the actuator housing with respect to the valve body necessitates a relatively long portion of the stem extending between the valve and the actuator housing. This increases the profile of the valve-actuator combination and also makes it necessary to provide a shroud or bonnet to cover this portion of the stem and to rigidly connect the valve body to the actuator housing.